The present invention relates to a method for producing a stable preparation of nicorandil [N-(2-hydroxyethyl)nicotinamide nitrate (ester)] that will be very useful as a drug. More particularly, the present invention relates to a method for producing a stable nicorandil preparation containing a finely divided sugar and/or a powdery organic acid as an excipient.
The stability of drugs is dependent on various factors such as temperature, humidity, light and oxygen. Many proposals have heretofore been made with a view to producing stable drug preparations.
Nicorandil which is to be produced in a stable form by the present invention has coronary vasodilative and coronary vasoconstriction suppressing actions and is useful as a curative for various types of angina pectoris while causing minimum effects on the dynamics of cardiovascular circulation and on cardiac functions (see Japanese Patent Publication No. 17463/1983 and Unexamined Published Japanese Patent Application No. 9323/1978).
However, nicorandil preparations are not stable against the compressive pressure exerted by punching operations in tablet making and will experience a time-dependent decrease in the amount of the active principle. Conventional practice employed to avoid this problem is to coat the nicorandil crystal with stearyl alcohol or other coating materials (Unexamined Published Japanese Patent Application No. 145659/1982).
Nicorandil preparations which are fairly stable in the dry state but instable in humid conditions and must be produced and stored with special care being taken to avoid direct contact with moisture by, for example, wrapping in a completely moistureproof package which, however, is quite expensive.